1. Field of the Invention
The invention relates to ATM switches. More particularly, the invention relates to methods and apparatus for collecting and processing billing information in ATM networks.
2. State of the Art
The modern telecommunications infrastructure is moving rapidly toward adopting an ATM (asynchronous transfer mode) standard. The ATM technology has been evolving for many years and is continuing to evolve. While many aspects of ATM technology have been agreed upon, many are still in relatively early stages of development. For example, since ATM technology is only recently being deployed for commercial use, there are no agreed upon standards for collecting billing information from an ATM network.
Presently, all of the operations, administration, and maintenance (OAM) of an ATM network is accomplished pursuant to an interim specification which provides for two types of management information base (MIB). The first MIB is the interim local management interface (ILMI) MIB which is utilized at a user network interface (UNI). The second MIB is the ATM MIB which is utilized at a network to network interface (NNI) between ATM switches. According to the interim specification, access to the MIB information is provided via the Simple Network Management Protocol (SNMP). The MIBs are implemented by a management entity which resides at the interface and which contains an SNMP agent and typically a management application.
The MIBs each contain several groups of information, each group being stored as a table in RAM at the management entity. For example, the ILMI MIBs include tables for a physical group, an ATM layer group, a layer statistics group, VPC and VCC groups, and network prefix and address groups. The ATM MIBs include tables for an interface configuration group, a DS3 PLCP group, a TC sublayer group, VPL and VCL groups, VP and VC cross-connect groups, and the AAL5 connection performance statistics group.
According to various schemes being implemented presently, accounting information is derived from statistics stored in MIBs. The accounting information is then used to create billing information in order to bill customers for use of the ATM network. Generally, a separate billing MIB is provided for each slot controller (interface) in an ATM switch. Each billing MIB typically includes 500 entries (also referred to as records or rows). In order to gather the statistics from the MIBs, a "billing collector" entity must communicate with the ATM switch(es) using the SNMP protocol and gather data from each MIB. The SNMP protocol requires that information be retrieved from MIB tables one record at a time. For example, a typical sequence of SNMP commands from a billing collector involves repeated use of the GET command as illustrated in the code listing below.
______________________________________ repeat SNMP GET-Has slot restarted since last poll period SNMP GET-how many available records while (outstanding records) ( SNMP GETNEXT-First row in table save record to file SNMP GET-Delete first row ) wait (poll.sub.-- period) ) ______________________________________
This is a tedious procedure which taxes the processing resources in the ATM switches because it is relatively time consuming. This is further exacerbated by the fact that the MIBs are stored in RAM. The entries in the billing table will roll over and be lost if not read before the table fills. Therefore, the entries must be accumulated from the MIBs in a timely manner.